SETI

Science Heresy - November 2010


Spectrum of Cosmic Noise in the Microwave Region


SETI - The Search for Extraterrestrial Intelligence

Yes there's life, Jim, but not as we know it - Star Trek


SETI

Wikipedia: Search for Extra-Terrestrial Intelligence (SETI) is the collective name for a number of activities people undertake to search for intelligent extraterrestrial life. SETI projects use scientific methods to search for electromagnetic transmissions from civilizations on distant planets.

But how are we to know when an electromagnetic transmission from space is indeed a transmission from a civilization on a different planet? A human voice reciting "Mary had little lamb" would not be evidence because we do not expect a distant civilization to share our language and our culture. It has been suggested that we should look for a readily interpreted numerical code representing some mathematical truth of which only a civilized entity would be aware. For example, a prime number "Morse Code": 2 dots, then 3 dots, then 5, then 7, then 11, then 13, then 17, then 19, then 23, then 29, then 31. The absence of multiplies of 2,3 and 5 would indicate that the sender somehow knows about prime numbers. It is unlikely that any natural mechanism could generate such a sequence. On the other hand why would we expect anyone to spend millions of years transmitting sequences of prime numbers into space? We don't do it - why would they? (Well, we did once - see Arecibo message)

Okay then, perhaps we should look for "accidental" transmissions, i.e. transmissions which are a by-product of civilized behaviour. This in fact is what SETI does. It is based on the presumption that members of a distant civilization will communicate among themselves using radio waves pretty much as we do. Perhaps we can detect their mobile phones and their broadcast radio and television channels.

When we direct a radio telescope outwards to the Galaxy like a gigantic listening ear (actually a radio telescope is a type of a thermometer). It will pick up cosmic noise This cosmic noise is primarily stochastic, i.e. it has a continuous spectrum with some discrete lines in it due to radiation from known atoms and molecules such as hydrogen. These occur exactly where we expect to find them and have nothing to do with intelligent life.

The modus operandi of SETI is to look for discrete "signals" with line spectra which do not correspond to the line spectra of known chemicals. Thus SETI is concerned with the Deterministic-Stochastic Dichotomy. It is assumed that the detection of a determistic signal against a stochastic background spectrum is sufficient evidence of civilization.

SETI has been operating for nearly 50 years now and has found nothing.

This is hardly surprising. Even if there were civilizations out there similar to our own, their broadcast stations would not be detected by SETI for the simple reason that insufficient power would be transmitted.

Wikipedia: The search was sensitive enough to pick up transmitters with 1 GW EIRP (equivalent isotropically radiated power) to a distance of about 200 light years.

A transmitter putting out this sort of power would need to have a highly directional antenna beam. Because any planet must be rotating, the beam must sweep past the receiver too rapidly for it to be detected by the SETI method. A "non-beaming" or omnidirectional antenna emitting this sort of power on earth (assuming one could be built) would fall foul of regulatory authorities such as the FCC because of the interference it would generate. A large number of lower power transmissions serves humanity's needs better than does a single, monstrous radio beacon. This is the likely situation in any society which uses the electromagnetic spectrum for communication purposes.

Ironically, powerful radio beams sweeping past the earth are routinely detected by radio astronomers. They are known as pulsars. Pulsars are not considered to be evidence of alien civilizations.

A further problem is SETI's anthropomorphic (i.e. parochial) view of alien technology. SETI was conceived in the age of the superheterodyne receiver in which information is propagated by modulating a discrete frequency called the "carrier". This is very much a 20th century on Planet Earth phenomenon and is related to the ready availability of high conductivity metals such as copper and silver with which to build the required resonant circuitry. There is no reason to assume that a civilization on another planet would develop its communications in this particular way or, having done so, that such a communication system would continue to be used for more than a century or so.

But the real issue with SETI is that it is really "old hat". The world, and science, have moved on. The giant strides made by microbiology and genetics over the last half-century mean that we now know a good deal more about life and how life works at a chemical level than was dreamed possible when SETI started out. In particular we now have a much clearer understanding of the role played by viruses (rather than spontaneous mutations) in the evolution of species.

The hot topic today is Cosmic Ancestry, the new theory pertaining to evolution and the origin of life on Earth. It holds that life on Earth was seeded from space, and that life's evolution to higher forms depends on genetic programs that come from space. It is a wholly scientific, testable theory for which evidence is accumulating.

Closely related is the concept of panspermia the hypothesis that life exists throughout the Universe, distributed by meteoroids, asteroids, and planetoids.

Panspermia proposes that life that can survive the effects of space, such as extremophile bacteria, become trapped in debris that's ejected into space after collisions between planets that harbor life and Small Solar System Bodies (SSSB). Bacteria may travel dormant for an extended amount of time before colliding randomly with other planets or intermingling with protoplanetary discs. If met with ideal conditions on the new planets' surfaces, the bacteria become active and the process of evolution begins.

Panspermia implies that life is ubiquitous in the universe and, indeed, that evolution on earth continues to be moulded by viruses arriving here from space.



A Modest Proposal

We propose that supposedly sterile, extra-terrestrial objects such as the interior of meteorites and samples of lunar soil brought back by the Apollo program, be subjected to analysis using the polymerase chain reaction (PCR) so that fragments of DNA or RNA can be amplified to manageable quantities and further analysed. If no DNA or RNA is found, then the panspermia theory can be abandoned and we must look for extraterrestrial life in some other way or presume that the earth is indeed unique with respect to the existence of life.



Image from NASA report SP-419: SETI - the Search for Extraterrestrial Intelligence



November 2010

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